People forget the slavery and racism in the north. Plenty of northerners supported slavery and 4 or 5 states in the union where slave states until the 13th ammendment. Licoln himself said he would keep slavery if he thought it would preserve the union. That seems to imply that slavery was not the central issue on either side. Lincoln also wanted to deport the emacipated slaves after the war.
You have to wonder where 75% of southerners, not even owning slave, would be willing to send the fathers, sons, brothers and sometimes grandfathers and children off to fight and die for the right to own slaves?
The founding fathers owned slaves yet we don't consider their flag a racist symbol.Crappy history books try to simplify a complicated war by boiling it down to one issue.